cc: Disable flaky perftest pending investigation.

This disables update tile priority tests, since it seems to be
excessively noisy. We need to investigate this, but for now this
disables the test.

BUG=310220
R=enne@chromium.org

Review URL: https://codereview.chromium.org/38393003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230609 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230609